1. Field of the Invention
The present invention relates generally to an enzymatic mediated copolymerization process of hydroxytyrosol with different flavonoids which results in a novel polymer of polyphenol. This polymer has improved electrical and optical properties, water solubility, and consequently processability (compared to phenolic resins) and may be synthesized using chemically safe and environmentally friendly conditions for the formation of antioxidant for foods or anticancer drugs.
2. Description of the Related Art
Naturally occurring flavonoids have attracted a great deal of attention in the last decade primarily due to their potent antioxidant activity. In particular, compounds like catechins belonging to the flavonoid family have been found to possess very good antioxidant activity. These flavonoids are naturally occurring and are found in green and white teas, cocoa, red wine, strawberries, cherries, peaches, apples, plums, beans and lentils. Common catechins are: (+)-catechin, (−)-catechin, (−)-epicatechin, epicatechin gallate (ECG), and epigallocatechin-3-gallate (EGCG). In a recent study, the addition of 300 mg/Kg catechin showed inhibition of oxidation in red meat and poultry.
Moreover, catechins were found more effective against lipid oxidation in raw pork compared to BHA and BHT. However, the commercial use of catechins as antioxidants has been impeded by their poor thermal stability. Flavonoids like EGCG are known to decompose at room temperature after a few minutes. Curcumin decomposes at room temperature in aqueous solution. Other flavonoids, like epicatechins, decompose at temperatures beyond 45° C. One objective is to overcome the limitations of the naturally occurring flavonoids to render them more stable through polymerization. To accomplish this, we propose a unique and simple one-pot synthesis to make copolymeric flavonoids that exhibit enhanced stability and activity over the naturally occurring forms. This novel approach will involve the use of flavonoids, isolated from naturally occurring materials that will be polymerized using oxidoreductases such as horseradish peroxidase (HRP).
Enzymatic polymerization of phenol in aqueous solutions was initially investigated as a possible benign and environmentally friendly solution to the synthesis of polyphenols (J. A. Akkara, K. J. Senecal, and D. L. Kaplan, Jour. of Pol. Part A: Pol. Chem., 29, 1561, (1991)).
These initial attempts were unsuccessful as only very low molecular weight oligomers could be formed which had limited properties to meet the requirements for such applications. Alternative enzymatic reactions have since been investigated to improve molecular weight and the mechanical, thermal, optical and electronic properties of these polymers including micelles, air-water interface monolayers and mixture into various organic solvents. Although the molecular weights and properties of these polyphenols were improved, their commercial application remains limited due to extensive branching and poor solubility and processability of the resulting polymers (Madhu S. Ayyagari, Kenneth A. Marx, Sukant K. Tripathy, Joseph A. Akkara, and David L. Kaplan: “Controlled Free-Radical Polymerization of Phenol Derivatives by Enzyme-Catalyzed Reactions in Organic Solvents” Macromolecules 1995, 28, 5192).